THE METHODS TO AVOID THE FORMATION OF METALLIC SILICIDE AT THE INTERFACE OF METAL/SILICON NITRIDE, AND THEIR APPLICATION FOR JOININGS

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THE KINETICS AND MECHANISM OF HIGH TEMPERATURE REACTIONS OF METALS WITH SILICON NITRIDE WERE INVESTIGATED. IT WAS THE PURPOSE OF THE PRESENT INVESTIGATION TO DESCRIBE THE CONDITIONS TO FORM NO BRITTLE PRODUCTS AT THE INTERFACE OF METAL/SILICON NITRIDE. THE PAUCITY OF REPORTS ON MECHANICAL PROPERTIES OF SOME METAL SILICIDES AND THE SOLID SOLUTIONS OF METAL AND SILICON SYSTEMS PROMPTED US TO INVESTIGATE THEM. MECHANICAL STRENGTH, YOUNG'S MODULUS AND LINEAR THERMAL EXPANSION COEFFICIENTS OF THE SILICIDES AND SOLID SOLUTIONS WERE MEASURED. BECAUSE THE SOLID SOLUTIONS WERE DUCTILE THEY APPEARED TO BE SUITABLE FOR JOINING. USING PLATE LIKE SAMPLES OF METALS AND SILICON NITRIDE, THE REACTION LAYERS WERE OBSERVED. IN THE CASE OF NICKEL, ONLY A SOLID SOLUTION LAYER WAS FORMED WITHOUT ANY SILICIDES AT 1273 K AND 1373 K. METALS SILICIDE LAYERS WERE FORMED IN THE CASES OF IRON AND COBALT EVEN AT 1173 K. THE SILICON CONTENT OF NICKEL SOLID SOLUTION WERE VERY LOW AND ITS DISTRIBUTION WAS UNIFORM. AND THE REACTION KINETICS OBEYED THE LINEAR RATE LAW. THUS, THE RATE DETERMINING STEP WAS THE DECOMPOSITION REACTION OF SILICON NITRIDE. THE REACTION RATE CONSTANT CAN BE EXPRESSED AS FOLLOWS: k(ms^<-1>) = 2.0 x 10^<-4> exp(-165kJmol^<-1>/RT). USING POWDERED METAL-SILICON NITRIDE MIXTURES, THE REACTION BEHAVIORS WERE OBSERVED BY MEANS OF MEASUREMENTS OF THE LIBERATED NITROGEN DURING THE REACTIONS. THE RESULTS OF THE EXPERIMENTS AGREED APPROXIMATELY WITH THOSE OF BLOCK SAMPLES. FURTHERMORE, THE ALLOYING ELEMENTS SUCH AS ALUMINUM, TITANIUN AND CHROMIUM IN NICKEL ALLOY PROMOTED THE DECOMPOSITION OF SILICON NITRIDE. BUT, THE LARGE AMOUNTS OF THEM HAD A BAD EFFECT ON THE SOLID-SOLUTION FORMATIONS TO FORM NITRIDE AND SILICIDE OF THE ALLOYING ELEMENTS.